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Abstract: Aegilops cylindrica Host (jointed goatgrass) is an exotic invasive weed in the western United States that causes economic loss due to competition with winter wheat (Triticum aestivum L.) and contamination of wheat grain. Further, because Ae. cylindrica is a wild relative of wheat, interspecific hybridization is a possible mechanism for the introgression of advantageous genes from wheat to the weedy species. The risk of introgression of traits conferring environmental stress tolerance, such as drought tolerance, from transgenic wheat has not been studied and is of high concern because it could increase the weed''s competitiveness with wheat, as well as its ability to invade novel habitats. Genetic diversity has been reported among western U.S. Ae. cylindrica accessions, however, studies to determine whether genetic diversity relates to phenotypic diversity have been limited. Here, 30 accessions of Ae. cylindrica from the western U.S. were evaluated over two years at two Colorado locations: Haxtun in 2008–2009 and Fort Collins in 2009–2010. Days to flowering, plant height, number of tillers produced per plant, number of spikelets per spike, and number of spikelets per plant were evaluated under rain-fed and irrigated conditions. Results indicate significant (P <0.01) variation among accessions for each of the traits for both years. Additionally, in 2009–2010 there was a significant (P <0.01) effect of irrigation on all traits, except days to flowering. Similarly, all traits except days to flowering showed a significant effect of the interaction of accession with treatment (P <0.05) in 2009–2010. The study shows that variation exists in traits related to competitive ability and fitness. Our data also suggest differences among accessions in sensitivity to water availability. This observation needs to be confirmed in additional environments. Implications of our results for evaluation of transgene introgression are discussed. [Copyright &y& Elsevier]

Abstract: One-year winter wheat–summer maize rotation is the most popular double cropping system in north-central China, and this highly productive system is an important source of nitrous oxide (N2O) and nitric oxide (NO) emissions due to the high fertilizer N and irrigation water inputs. To sustain the high crop production and mitigate the detrimental impacts of N2O and NO emissions, improved management practices are extensively applied. The aim of this study is therefore to evaluate the effects of an improved management practice of irrigation, fertilization and crop straw on grain yield and N2O and NO emissions for a wheat–maize rotation field in northern China. Using automated and manual chamber measuring systems, we monitored N2O and NO fluxes for the conventional (CT, 2007–2008), improved (IT, 2007–2008), straw-amended (WS, 2008–2009), straw-not-amended (NS, 2008–2009), and no N-fertilizer treatments (WS–NN, 2008–2009), respectively, for one rotation-year. The grain yields were determined for CT and IT for three rotation-years (2005–2008) and for WS, NS and WS–NN for one rotation-year (2008–2009). The improved management of irrigation and fertilization reduced the annual N fertilization rate and irrigation amount by 17% and 30%, respectively; increased the maize yield by 7–14%; and significantly decreased the N2O and NO emissions by 7% (p <0.05) and 29% (p <0.01), respectively. The incorporation of wheat straw increased the cumulative N2O and NO emissions in the following maize season by 58% (p <0.01) and 13%, respectively, whereas the effects of maize straw application were not remarkable. The N2O and NO emission factors of applied N were 2.32±2.32% and 0.42±1.69% for wheat straw and 0.67±0.23% and 0.54±0.15% for chemical N-fertilizers, respectively. Compared to conventional management practices using high application rates of irrigation water and chemical N-fertilizer as well as the field burning of crop straw, the improved management strategy presented here has obvious environmentally positive effects on grain yield and mitigation of N2O and NO emissions. [Copyright &y& Elsevier]

Methane (CH4) is one of the important greenhouse gases accounting for 15% of the total enhanced greenhouse effect. Rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system is the most dominating cropping system in the Indo-Gangetic plains (IGPs) of India occupying 10.5 million ha of productive land could be a major source of atmospheric CH4. Effect of irrigation, urea, farmyard manure (FYM), and dicyandiamide (DCD) on emission of CH4 from an alluvial soil (Ustochrept) in rice–wheat cropping system was studied using the closed chamber technique. Total emission of CH4 from the rice–wheat systems ranged from 16.2 kg ha−1 in the control treatment to 36.5 kg ha−1 in urea plus FYM treatment with an average emission of 20.8 kg CH4 ha−1. Continuously saturated soil in rice gave higher CH4 emission compared to intermittent wetting and drying soil condition but the yields were lowered. Application of DCD with urea reduced emission of CH4 in rice–wheat system to 70%, while substituting 50% of inorganic N with FYM increased emission to 172% compared to application of entire amount of N through urea. In wheat negative fluxes of CH4 up to 0.1 kg ha−1 per day was recorded. There was no difference in CH4 flux in wheat between the various irrigation treatments. In the most common fertilizer practice in IGPs the emission of CH4 is 21.2 kg ha−1. Intermittent wetting and drying of soil in rice has a potential to reduce the emission. [Copyright &y& Elsevier]

• Crop pest herbivores and their parasitoids significantly impact wheat yield. • Cascading effects of parasitoids on yield were consistent across precipitation levels. • Tri-trophic interactions can be robust to large shifts in a major climate driver. Changing climatic conditions can fundamentally alter the interactions between species with important implications for agriculture. The impacts of shifts in precipitation on trophic interactions have been understudied relative to other climate drivers. We carried out field experiments to examine how precipitation, attack by parasitoid wasps (Bracon cephi (Gahan))(Hymenoptera: Braconidae) and their potential interaction affect the performance of a major pest of wheat, Cephus cinctus Norton (Hymenoptera: Cephidae), and its impact on wheat yield. We independently manipulated insects (no insects, + C. cinctu s, or + C. cinctus and B. cephi) and precipitation (-50% to -70%, ambient, +70%) in a factorial design in each of two growing seasons. Crop-herbivore-parasitoid interactions were remarkably robust to our precipitation manipulations with no significant changes in C. cinctus infestation, survival or levels of parasitism observed in the first (wetter) year of the study. Despite slight declines in pest infestation and percent parasitism under precipitation addition relative to reduction in the second year, both insects had strong and significant impacts on crop yield. These effects were consistent across precipitation manipulations, as evidenced by the lack of a significant interaction between insect and precipitation treatments. The results suggest that natural enemy benefits to crop production in this system can be substantial, and are likely to be robust across a relatively wide range of precipitation levels. While rare, studies that examine climate influences within a tri-trophic context are critical to predicting how pest insects will ultimately impact crop production under changing climatic conditions. [ABSTRACT FROM AUTHOR]